How does the author provide information or details to make the story seem realistic?

I always find the city of London to lend both realism and mystery to the story. The novel begins on a London street that proves to act as central to much of the novel's action. The descriptions of the city vary, from idyllic and majestic to dangerous, mysterious and dark. In Victorian London, the modern city began to powerfully establish itself. In his afterword to the novel, Dan Chaon notes that Stevenson relied on the modern city in order to provide a realistic location in which Hyde could live. Chaon explains, "[Hyde] needs the anonymity of the masses, ad he needs the newly gaslit streets, the flickering nighttime landscape of pubs and brothels and beggards, the urban underworld that would later transform into the world of film noir." Thus, the growing and developing city of London gave Hyde a cloak in which to hide his despicable behavior, and gave him precious anonymous freedom. In this world, Hyde was able to walk through society unnoticed and disregarded by the many strangers who roamed the streets. Without this opportunity for absolute anonymity, Jekyll would never have been able to carry out his experiment. Thus, the bustling, growing and many layered city of London supported Jekyll's work and gave him the freedom to pursue his dual lives.